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Research in the Physical Geodesy of Louisiana Subsidence

Research in the Physical Geodesy of Louisiana Subsidence. Cliff Mugnier Chief of Geodesy Louisiana Spatial Reference Center LOUISIANA STATE UNIVERSITY cjmce@LSU.edu. 1976-77 NGS Leveling (funded by Corps of Engineers). Start at Index, Arkansas, through Simmsport, LA to:

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Research in the Physical Geodesy of Louisiana Subsidence

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  1. Research in the Physical Geodesy of Louisiana Subsidence Cliff Mugnier Chief of Geodesy Louisiana Spatial Reference Center LOUISIANA STATE UNIVERSITY cjmce@LSU.edu

  2. 1976-77 NGS Leveling (funded by Corps of Engineers) • Start at Index, Arkansas, • through Simmsport, LA to: • Morgan City & Baton Rouge, both then to: • New Orleans, thence to: • Venice, LA (spur) and Logtown, MS to close the line. • … and $1,500,000.00 later,

  3. Surprise! There’s subsidence way down yonder … • Allowable misclosure for 530 kilometers of levels was 92 mm, • Actual misclosure was 86 mm, but • Too much error manifested in Metro New Orleans to close locally. • 1978 National Geodetic Survey changes name from SLD 1929 to NGVD 1929 • Let’s do a “Regional Paper Adjustment.”

  4. 1982-83 NGS Regional Adjustment of South Louisiana Catastrophic Floods of : May 3, 1979; April 12-13, 1980 • Orleans, Jefferson, and Plaquemines Parishes funded NGS to re-observe BMs. • Corps of Engineers concerned with the “NGS FREE ADJUSTMENT” • Deep casement marks introduced

  5. Local Governments fund Geodetic Surveys in 1986-88 • Jefferson Parish Benchmark System • Entire East Bank • Metro West Bank and south to Lafitte • Relative gravity observed at ~350 benchmarks • St. Bernard Parish Benchmark System • IHNC to Reggio • Relative gravity observed at ~100 benchmarks

  6. North American Vertical Datum of 1988 Actual published data available starting in 1990 No data available for South Louisiana (Crustal Motion Area)

  7. FG-5 Absolute Gravity Meter(±1μgal)

  8. Absolute Gravity Observed in New Orleans: March, 1989 979,316,847.7 mgals Sept., 1991 979,316,854.2 mgals (-0.91 centimeters per year)

  9. 1991 – Fall of the Soviet Union • In December of 1991, as the world watched in amazement, the Soviet Union disintegrated into fifteen separate countries. Its collapse was hailed by the west as a victory for freedom, a triumph of democracy over totalitarianism, and evidence of the superiority of capitalism over socialism. The United States rejoiced as its formidable enemy was brought to its knees, thereby ending the Cold War which had hovered over these two superpowers since the end of World War II. Indeed, the breakup of the Soviet Union transformed the entire world political situation, leading to a complete reformulation of political, economic and military alliances all over the globe.

  10. National Geodetic Survey returns to New Orleans • 1991-92 Field Observations in “support” of Orleans Parish GeoCadastre • Lines tied to: • J-92 (Rigolets Bridge) • Vets Blvd. @ Orleans Parish Line

  11. 1993 Adjustment by NGS for Subsidence Zone Elevations • Last visit to New Orleans for the century • National Geodetic Survey loses funding for Long Line Leveling Crew • GPS Constellation continues to grow • Defense Mapping Agency downgrades security classification on the GEOID

  12. Absolute Gravity Observed in New Orleans: Nov., 1993 979,316,856.3 mgals Aug., 1994 979,316,860.6 mgals (-0.91 centimeters per year)

  13. 1996Defense Mapping Agency awards $1,000,000 contract to re-compute the GEOID

  14. Subsidence

  15. Absolute Gravity Observations • In 2002: • UNO (5th time) • Stennis Space Center (2nd) • Loyola University • Southeastern Louisiana Univ. • LSU • McNeese State Univ. • Venice-Boothville H.S. • LUMCON @ Cocodrie • Oakdale H.S. • LSU Alexandria • Old River Aux. Control Structure • Nicholls State Univ. • Univ. of Louisiana in Lafayette • Northwestern State Univ. • Sicily Island H.S. • LSU Shreveport • Louisiana Tech Univ. • In 2006: • UNO (6th time) • Stennis Space Center (3rd) • Loyola University (2nd) • Southeastern Louisiana Univ. (2nd) • LSU (2nd) • McNeese State Univ. (2nd) • Venice-Boothville H.S. (2nd) • LUMCON @ Cocodrie (2nd) • Oakdale H.S. (2nd) • LSU Alexandria (2nd) • Old River Aux. Control Structure (2nd) • Nicholls State Univ. (2nd) • Univ. of Louisiana in Lafayette (2nd) • Grand Isle U.S.C.G. Station • Lamar Univ. in Beaumont • Univ. of Mississippi in Hattiesburg

  16. By 2019, • Absolute Gravity Observed at CORS : • By NGA: 15 • By LSRS: 22 • Remaining: 17 • (plus TX, MS, AL) • Results so far … • Old River -34mm • Lake Charles -16 mm • LUMCON -20 mm • Boothville -13 mm • Alexandria -49 mm • Ruston -9 mm • (All since 2002)

  17. The Baton Rouge Fault -5mm/yr

  18. Current Objectives at LSRC • 1. Continue observation of Absolute Gravity at all LSRC CORS sites • 2. Commence observation of Deflection of the Vertical at all LSRC CORS sites • 3. Continue GIPSY Processing of all LSRC Historical CORS sites for correlation • 4. Continue providing data to NGS

  19. R.S. 50:173.1 Questions? Cliff Mugnier cjmce@LSU.edu (225) 578-4578

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